Process for forming deposited film by use of alkyl aluminum hydride

ABSTRACT

A process for forming an Al film of good quality according to the CVD method utilizing the reaction between alkyl aluminum hydride and hydrogen, which is an excellent deposited film formation process also capable of selective deposition of A1.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a process for forming a deposited film,particularly a process for forming an Al deposited film which can bepreferably applied to electrodes or wiring of a semiconductor integratedcircuit device, etc.

2. Related Background Art

In the prior art, in electronic devices or integrated circuits by use ofsemiconductors, for electrodes and wiring, aluminum (Al) has beenprimarily used. Al has many advantages such that it is inexpensive andhigh in electroconductivity, that it can be also internally chemicallyprotected because a dense oxidized film can be formed on the surface,and that it has good adhesion to Si, etc.

As the method for forming Al film for electrodes and wiring of Al or Alalloy as mentioned above, there has been used in the prior art thesputtering method such as magnetron sputtering, etc. However, since thesputtering is generally the physical deposition method based on flyingof sputtered particles in vacuum, the film thickness at the steppedportion or the insulating film side wall becomes extremely thin, leadingto wire breaking in an extreme case. Nonuniformity of film thickness orwire breaking has the drawback that reliability of LSI is markedlylowered.

On the other hand, since the integration degree of the integratedcircuit such as LSI, etc. is increased, and fine formation of wiring ormulti-layer wiring has been particularly required in recent years, thereis an increasing severe demand not found up to date for Al wiring of theprior art. With finer dimensional formation by increased integrationdegree, the surface of LSI, etc. is subject to excessive unevenness dueto oxidation, diffusion, thin film deposition, and etching, etc. Forexample, electrodes or wiring metal must be deposited on the surfacewith a stepped difference, or deposited in a via-hole which is fine indiameter and deep. In 4 Mbit or 16 Mbit DRAM (dynamic RAM), etc., theaspect ratio (via-hole depth/via-hole diameter) or via-hole in which ametal composed mainly of Al such as Al, Al-Si, etc. is to be depositedis 1.0 or more, and the via-hole diameter itself also becomes 1 μm orless. Therefore, even for a via-hole with large aspect ratio, thetechnique which can deposit a metal is required.

Particularly, for performing sure electrical connection to the deviceunder insulating film such as SiO₂, etc., rather than film formation, Alis required to be deposited so as to embed only the via-hole of thedevice. In such case, a method of depositing Al only on Si or metalsurface and not depositing it on an insulating film such as SiO₂, etc.is required.

Such selective deposition or selective growth cannot be realized by thesputtering method which has been used in the prior art. Since thesputtering method is a physical deposition method based on flying of theparticles sputtered from the target in vacuum, the film thickness at thestepped portion or the insulating film side wall becomes extremely thin,leading even to wire breaking in an extreme case. And, nonuniformity ofthe film thickness and wire breaking will markedly lower reliability ofLSI.

As the improved sputtering method, there has been developed the biassputtering method in which a bias is applied on a substrate anddeposition is performed so as to embed Al or an Al alloy only in thevia-hole by utilizing the sputter etching action and the depositionaction on the substrate surface. However, since the bias voltage of some100 V or higher is applied on the substrate, deleterious influence onthe device occurs because of charged particle damaging such as change inthreshold of MOS-FET, etc. Also, because of presence of both etchingaction and deposition action, there is the problem that the depositionspeed cannot be essentially improved.

In order to solve the problems as described above, various types of CVD(Chemical Vapor Deposition) methods have been proposed. In thesemethods, chemical reaction of the starting gas in some form is utilized.In plasma CVD or optical CVD, decomposition of the starting gas occursin gas phase, and the active species formed there further reacts on thesubstrate to give rise to film formation. In these CVD methods, due tothe reaction in gas phase, surface coverage on unevenness on thesubstrate surface is good. However, carbon atoms contained in thestarting gas molecule are incorporated into the film. Also, particularlyin plasma CVD, the problem remained that there was damage by chargedparticles (so called plasma damage) as in the case of the sputteringmethod.

The thermal CVD method, in which the film grows through the surfacereaction primarily on the substrate surface, is good in surface coverageon unevenness such as stepped portion of the surface, etc. Also, it canbe expected that deposition within via-hole will readily occur. Further,wire breaking at the stepped portion can be avoided.

For such reasons, as the formation method of Al film, the thermal CVDmethod has been variously studied. As the formation method of Al filmaccording to general thermal CVD, there is used a method of transportingand organic aluminum dispersed in carrier gas to a heated substrate andpyrolyzing the gas molecules on the substrate to form a film. Forexample, in an example seen in Journal of Electrochemical Society, Vol.131, p. 2175 (1984), by use of triisobutyl aluminum (i--C₄ H₉)₃ Al(TIBA) as organic aluminum gas, film formation is effected at a filmformation temperature of 260° C. and a reaction tube pressure of 0.5torr to form a film of 3.4 μohm.cm.

Japanese Laid-open Patent Application No. 63-33569 describes a method offorming a film by using no TiCl₄, but using in place thereof organicaluminum such as TIBA and heating it in the vicinity of the substrate.According to this method, Al can be deposited selectively only on themetal or semiconductor surface from which the naturally oxidized filmhas been removed.

In this case, it is clearly stated that the step of removing thenaturally oxidized film on the substrate surface is necessary beforeintroduction of TIBA. Also, it is described that, since TIBA can be usedalone, no carrier gas is required to be used, but Ar gas may be alsoused as the carrier gas. However, the reaction of TIBA with another gas(e.g. H₂) is not contemplated at all, and there is no description of useof H₂ as the carrier gas. Also, in addition to TIBA, trimethyl aluminum(TMA) and triethyl aluminum (TEA) are mentioned, but there is nospecific description of other organic metals. This is because, since thechemical properties of organic metals generally vary greatly if theorganic substituent attached to the metal element varies little, it isnecessary to investigate individually by detailed experimentation todetermine what organic metal should be used.

In the CVD method as described above, not only there is an inconveniencethat the naturally oxidized film must be removed, but also there is thedrawback that no surface smoothness can be obtained. Also, there is therestriction that heating of the gas is necessary, and yet heating mustbe done in the vicinity of the substrate. Besides, it must also beexperimentally determined at what proximity to the substrate heatingmust be done, whereby there is also the problem that the place forsetting the heater cannot be necessarily freely chosen.

In the pre-text of the 2nd Symposium of Electrochemical Society, Branchof Japan (Jul. 7, 1989), on page 75, there is a description of filmformation of Al according to the double wall CVD method. In this method,TIBA is used and the device is designed so that the gas temperature ofTBA can be made higher than the substrate temperature. This method maybe also regarded as a modification of the above-mentioned JapaneseLaid-open Patent Application No. 63-33569. Also in this method, Al canbe selectively grown only on a metal or semiconductor, but not only thedifference between the gas temperature and the substrate surfacetemperature can be controlled with difficulty, but also there is thedrawback that the bomb and the pipeline must be heated. Moreover,according to this method, there are involved such problems that nouniform continuous film can be formed, that flatness of the film ispoor, that selectivity of Al selective growth cannot be maintained forso long time, etc., unless the film is made thick to some extent.

As described above, prior art methods cannot necessarily effect wellselective growth of Al, and even if possible, there is a problem withrespect to flatness, resistance, purity, etc. of the Al film formed.Also, there has been involved the problem that the film formation methodis complicated and can be controlled with difficulty.

SUMMARY OF THE INVENTION

As described above, in the technical field of semiconductors in whichhigher integration has been desired in recent years, for providinginexpensively a semiconductor device which is more highly integrated andalso made higher in performances, there remained ample room forimprovement.

The present invention has been accomplished in view of the technicaltasks as described above, and an object of the present invention is toprovide a process for forming a deposited film which can form an Al film(hereinafter referring comprehensively to pure Al and a metal composedmainly of Al) of good quality as the electroconductive material at adesired position with good controllability.

Another object of the present invention is to provide a process forforming a deposited film which can obtain an Al film which has extremelybroad general purpose utility and yet is of good quality, withoutrequiring particularly no complicated and expensive deposited filmforming device.

Still another object of the present invention is to provide a processfor forming a deposited film which can form an Al film excellent insurface characteristic, electrical characteristics, purity, etc.according to the CVD method utilizing alkyl aluminum hydride andhydrogen.

Still another object of the present invention is to provide a processfor forming a deposited film of an Al film which is extremely broad ingeneral purpose utility and excellent in selectivity, without requiringparticularly a complicated and expensive deposited film forming device.

Still another object of the present invention is to provide a processfor forming a deposited film which can form an Al film under goodselectivity according to the CVD method utilizing alkyl aluminum hydrideand hydrogen.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view for illustration of a suitable deposited filmforming device in practicing the deposited film forming processaccording to the process of the present invention.

FIG. 2 is a schematic view for illustration of another suitabledeposited film forming device in practicing the deposited film formingprocess according to the present invention.

FIGS. 3A-3E are schematic sectional views for illustration of thedeposited film forming process according to one embodiment of thepresent invention.

FIG. 4 is a chart showing the X-ray diffraction pattern of the Si (111)substrate having the Al film obtained according to the deposited filmforming process of the present invention.

FIGS. 5A and 5B are charts showing the X-ray diffraction pattern of theAl film on the Si (111) substrate obtained according to the depositedfilm forming process of the present invention.

FIG. 6 is a chart showing the X-ray diffraction pattern on the Si (100)substrate having the Al film obtained according to the deposited filmforming process of the present invention.

FIG. 7 is a schematic view for illustration of the scanning μ-RHEEDmethod.

FIG. 8 is a schematic view for illustration of the scanning μ-RHEEDmethod.

FIG. 9 is a chart showing another example of the X-ray diffractionpattern of the substrate having the Al film obtained according to theselective deposited film forming process of the present invention.

FIGS. 10A-10C are schematic views showing an example of the scanningsecondary electron image and the scanning μ-RHEED image of the substratehaving the Al film obtained according to the selective deposited filmforming process of the present invention.

FIG. 11 is a chart showing another example of the X-ray diffractionpattern of the substrate having the Al film obtained by the selectivedeposited film forming process of the present invention.

FIGS. 12A-12C are schematic views of another example of the scanningsecondary electron image and the scanning μ-RHEED image of the substratehaving the Al film obtained according to the selective deposited filmforming process of the present invention.

FIGS. 13A-13D are illustrations for explaining the mechanism of Aldeposition according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments according to the present invention are describedin detail below, but the present invention is not limited by theseembodiments, and it may have a constitution which accomplishes theobject of the present invention.

One preferred embodiment of the present invention is a process forforming a deposited film comprising the steps of:

(a) providing a substrate having an electron donative surface (A) in aspace for formation of the deposited film;

(b) introducing a gas of an alkyl aluminum hydride and hydrogen gas intothe space for formation of the deposited film; and

(c) maintaining the temperature of the electron donative surface (A)within the range of from the decomposition temperature of the alkylaluminum hydride to 450° C. to form an aluminum film on the electrondonative surface (A).

Further, another preferred embodiment of the present invention is aprocess for forming a deposited film comprising the steps of:

(a) providing a substrate having an electron donative surface (A) and aelectron non-donative surface (B) in a space for formation of thedeposited film;

(b) introducing a gas of an alkyl aluminum hydride and hydrogen gas intothe space for formation of the deposited film; and

(c) maintaining the temperature of the electron donative surface (A)within the range of from the decomposition temperature of the alkylaluminum hydride to 450° C. to form an aluminum film selectively on theelectron donative surface (A).

In the following, prior to detailed description, first, the process forforming a deposited film by use of an organic metal is outlined.

The decomposition reaction of an organic metal, and hence the thin filmdeposition reaction will vary greatly depending on the kind of the metalatom, the kind of the alkyl bonded to the metal atom, the means ofcausing the decomposition reaction to occur, the atmospheric gas, etc.

For example, in the case of M--R₃ (M: the group III metal, R: alkylgroup), trimethyl gallium: ##STR1## in thermal decomposition undergoesradical cleavage wherein Ga--CH₃ bond is cleaved, while triethylgallium: ##STR2## in thermal decomposition is decomposed throughβ-elimination into: ##STR3## and C₂ H₄. On the other hand, triethylaluminum attached with the same ethyl group: ##STR4## in thermaldecomposition undergoes radical decomposition in which Al--C₂ H₅ iscleaved. However, tri-iso-butyl aluminum having iC₄ H₉ bonded therein:##STR5## is subject to β-elimination.

Trimethyl aluminum (TMA) comprising CH₃ groups and Al has a dimerstructure at room temperature: ##STR6## and thermal decomposition isradical decomposition in which Al--CH₃ group is cleaved, and at atemperature of 150° C. or lower, it reacts with atmospheric H₂ to formCH₄, and forms finally Al.

However, at a high temperature of 300° C. or higher, even if H₂ may bepresent in the atmosphere, CH₃ group will withdraw H from the TMAmolecule, until finally Al-C compound is formed.

Also, in the case of TMA, in light or a certain region controlled inelectric power in H₂ atmosphere high frequency (ca. 13.56 MHz) plasma,C₂ H₆ will be formed by the bridging CH₃ between two Al's.

In essence, since even an organic metal comprising CH₃ group which thesimplest alkyl group, C₂ H₅ group or iC₄ H₉ group and Al or Ga has areaction mode depending on the kind of the alkyl group, the kind of themetal atom, the excitation decomposition means, for deposition of ametal atom from an organic metal on a desired substrate, thedecomposition reaction must be strictly controlled. For example, when Alis to be deposited from triisobutyl aluminum: ##STR7## in the lowpressure CVD method comprising mainly thermal reaction, unevenness onthe μm order is formed on the surface, whereby the surface morphology isinferior. Also, hillock generation by heat treatment, Si surfaceroughening through Si diffusion at the interface between Al and Sioccur, and also migration resistance is inferior, whereby it can beutilized for ultra-LSI process with difficulty.

For this reason, a method for controlling precisely both the gastemperature and the substrate temperature has been attempted. However,the device is complicated, and the method is of the sheet treatment typein which deposition can be effected only on one wafer by one depositionprocess. Besides, since the deposition speed is 500 A/min. at thehighest, the throughput necessary for bulk production cannot berealized.

Similarly, when TMA is employed, Al deposition has been attempted by useof plasma or light, the device also becomes complicated due to use ofplasma or light, and also because of the sheet type device, thereremains room for improvement for sufficient improvement of throughput.

Dimethyl aluminum hydride (DMAH) as the alkyl aluminum hydride to beutilized in the present invention is a substance known as alkyl metal,but it could not be estimated at all what Al thin film could bedeposited depending on what reaction mode, unless deposited films areformed under all the conditions. For example, in an example ofdeposition Al by optical CVD from DMAH, the surface morphology isinferior, and the resistivity value was greater than the bulk value (2.7μohm.cm) as several μohm to 10 μohm.cm, thus being inferior in filmquality.

Now, referring to the drawings, preferred embodiments of the presentinvention are described in more detail.

In the present invention, for depositing selectively an Al film of goodquality as the electroconductive deposition film on a substrate, the CVDmethod is used.

More specifically, by use of dimethyl aluminum hydride (DMAH): ##STR8##as alkyl aluminum hydride which is an organic metal or monomethylaluminum hydride (MMAH₂): ##STR9## as alkyl aluminum hydride as thestarting gas containing at least one atom which becomes the constituentof the deposited film, and H₂ as the reaction gas, an Al film is formedby gas phase growth with a gas mixture of these on a substrate.

As the substrate applicable in the present invention, a material havingan electron donative surface may be employed.

The electron donative material is described in detail below.

The electron donative material refers to one having free electronsexisting or free electrons intentionally formed in the substrate, forexample, a material having a surface on which the chemical reaction ispromoted through give-and-take of electrons with the starting gasmolecules attached on the substrate surface. For example, generallymetals and semiconductors correspond to such material. Those having verythin oxidized film on the metal or semiconductor surface are alsoincluded. For, with such thin film, the chemical reaction can occurbetween the substrate and the attached starting molecules.

Specifically, there may be included semiconductors such asmonocrystalline silicon, polycrystalline silicon, amorphous silicon,etc., binary system or ternary system or quaternary system III-Vcompound semiconductors comprising combinations of Ga, In, Al as thegroup III element and P, As, N as the group V element, or II-IV compoundsemiconducters, or metals themselves such as tungsten, molybdenum,tantalum, aluminum, titanium, copper, etc., or silicides of the abovemetals such as tungsten silicide, molybdenum silicide, tantalumsilicide, aluminum silicide, titanium silicide, etc., further metalscontaining either one of the constituent of the above metals such asaluminum silicon, aluminum titanium, aluminum copper, aluminum tantalum,aluminum silicon copper, aluminum silicon titanium, aluminum palladium,titanium nitride, etc.

On the substrate with such constitution, Al is deposited only throughsimple thermal reaction in the reaction system of the starting gas andH₂. For example, the thermal reaction in the reaction system betweenDMAH and H₂ may be basically considered as follows: ##STR10## DMAHassumes a dimer structure at room temperature. Also, with MMAH₂, a highquality Al film could be formed by thermal reaction as shown below inExamples.

Since MMAH₂ has low vapor pressure as 0.01 to 0.1 Torr at roomtemperature, a large amount of the starting material can be transportedwith difficulty, and the upper limit value of the deposition speed isseveral hundred Å/min. in the present embodiment, and preferably, it ismost desirable to use DMAH of which vapor pressure is 1 Torr at roomtemperature.

In another embodiment of the present invention, the CVD method is usedfor selective deposition of a good Al film as the electroconductivedeposition film on the substrate.

More specifically, as described above, by use of dimethyl aluminumhydride (DMAH) or monomethyl aluminum hydride (MMAH₂) and H₂ as thereaction gas, an Al film is selectively formed on the substrate by gasphase growth with a gas mixture of these.

The substrate applicable in the present invention has a first substratesurface material for formation of the surface on which Al is deposited,and a second substrate surface material on which no Al is deposited.And, as the first substrate surface material, a material having theelectron donative surface is used.

In contrast, as the material for forming the surface on which Al is notdeposited selectively, namely the material for forming the electronnon-donative surface, conventional insulating materials, oxidizedsilicon formed by thermal oxidation, CVD, etc., glass or oxidized filmsuch as BSG, PSG, BPSG, etc., thermally nitrided film, silicon nitridedfilm by plasma CVD, low pressure CVD, ECR-CVD method, etc.

FIG. 1 is a schematic view showing a preferable deposition film formingdevice for applying the present invention.

Here, 1 is a substrate for forming an Al film. The substrate 1 ismounted on a substrate holder 3 provided internally of the reaction tube2 for forming a space for formation of a deposited film which issubstantially closed to FIG. 1. As the material constituting thereaction tube 2, quartz is preferable, but it may be also made of ametal. In this case, it is preferable to cool the reaction tube. Thesubstrate holder 3 is made of a metal, and is provided with a heater 4so that the substrate mounted thereon can be heated. And, theconstitution is made so that the substrate temperature can be controlledby controlling the heat generation temperature of the heater 4.

The feeding system of gases is constituted as described below.

5 is a gas mixer, in which the starting gas and the reaction gas aremixed, and the mixture is fed into the reaction tube 2. 6 is a startinggas gasifier provided for gasification of an organic metal as thestarting gas.

The organic metal to be used in the present invention is liquid at roomtemperature, and is formed into saturated vapor by passing a carrier gasthrough the liquid of the organic metal within the gasifier 6, which isin turn introduced into the mixer 5.

The evacuation is constituted as described below.

7 is a gate valve, which is opened when performing evacuation of a largevolume such as during evacuation internally of the reaction tube 2before formation of the deposited film. 8 is a slow leak valve, which isused when performing evacuation of a small volume such as in controllingthe pressure internally of the reaction tube 2 during formation of thedeposited film. 9 is an evacuation unit, which is constituted of a pumpfor evacuation such as turbo molecular pump, etc.

The conveying system of the substrate 1 is constituted as describedbelow.

10 is a substrate conveying chamber which can house the substrate beforeand after formation of the deposited film, which is evacuated by openingthe valve 11. 12 is an evacuation unit for evacuating the conveyingchamber, which is constituted of a pump for evacuation such as turbomolecular pump, etc.

The valve 13 is open only when the substrate 1 is transferred betweenthe reaction chamber and the conveying space.

As shown in FIG. 1, in the starting gas gasifier 6 which is the gasformation chamber for forming the starting gas, the liquid DMAHmaintained at room temperature is bubbled with H₂ or Ar (or other inertgas) as the carrier gas to form gaseous DMAH, which is transported tothe mixer 5. The H₂ gas as the reaction gas is transported throughanother route into the mixer 5. The gases are controlled in flow ratesso that the respective partial pressures may become desired values.

In the case of forming a film by this device, the starting gas may be ofcourse MMAH₂, but DMAH with a vapor pressure enough to become 1 Torr atroom temperature is the most preferred. Also, DMAH and MMAH₂ may be usedin a mixture.

The deposited film formed at a substrate temperature of 160° C. to 450°C. by use of such starting gas and reaction gas, with a thickness of forexample 400 Å, has a resistivity at room temperature of 2.7-3.0 μohm.cmwhich is substantially equal to Al bulk resistivity, and is a continuousand flat film. At this time, the pressure during film formation can bechosen within the range from 10⁻³ Torr to 760 Torr. Also, even when thefilm thickness may be 1 μm, its resistivity is ca. 2.7-3.0 μohm.cm, anda sufficiently dense film can be formed also with a relatively thickerfilm. Also, the reflectance in the visible light wavelength region isapproximately 80%, whereby a thin film excellent in surface flatness canbe deposited.

The substrate temperature is desirably the decomposition temperature ofthe starting gas containing Al or higher, and 450° C. or lower asdescribed above, but specifically the substrate temperature of 200° to450° C. is more desirable, and when deposition is carried out under thiscondition, by making the DMAH partial pressure 10⁻⁴ to 10⁻³ Torr, thedeposition speed becomes very great as 100 Å/min. to 800 Å/min., wherebysufficient great deposition speed corresponding to the cost as the Aldeposition technique for ultra-LSI can be obtained.

A more preferable substrate temperature condition is 270° C. to 350° C.,and the Al film deposited under this condition is also stronglyorientatable and, even when subjected to the heat treatment at 450° C.for 1 hour, the Al film on the Si monocrystalline or Si polycrystallinesubstrate becomes a good Al film without generation of hillock, spike asseen in the film forming method of the prior art. Also, such Al film isexcellent in electro-migration resistance.

In the device shown in FIG. 1, Al can be deposited on only one sheet ofsubstrate in deposition for one time. Although a deposition speed of ca.800 Å/min. can be obtained, it is still insufficient for performingdeposition of a large number of sheets within a short time.

As the deposition film forming device for improving this point, there isthe low pressure CVD device which can deposit Al by simultaneousmounting of a large number of sheets of wafer. Since the Al filmformation according to the present embodiment utilizes the surfacereaction on the electron donative substrate surface, in the hot walltype low pressure CVD method wherein only the substrate is heated, Alcan be deposited on the substrate by use of DMAH and H₂.

The reaction tube pressure may be 0.05 to 760 Torr, desirably 0.1 to 0.8Torr, the substrate temperature 160° C. to 450° C., desirably 200° C. to400° C., the DMAH partial pressure 1×10⁻⁵ -fold to 1.3×10⁻³ -fold of thepressure in the reaction tube, and under such conditions, Al can be welldeposited on the electron donative substrate.

FIG. 2 is a schematic illustration showing a deposited film formingdevice to which such present invention is applicable.

57 is a substrate for formation of Al film. 50 is an outside reactiontube made of quartz for forming a space for formation of deposited filmsubstantially closed to the surrounding, 51 an innerside reaction tubemade of quartz located for separating the flow of gas within the outsidereaction tube 50, 54 a flange made of a metal for opening and closing ofthe opening of the outside reaction tube 50, and the substrate 57 islocated within the substrate holding member 56 provided internally ofthe innerside reaction tube 51. The substrate holding member 56 shouldbe preferably made of quartz.

Also, in the present device, the substrate temperature can be controlledby the heater portion 59. The pressure internally of the reaction tube50 is constituted so as to be controllable by the evacuation systemconnected through the gas evacuation outlet 53.

The gas feeding system is constituted to have a first gas system, asecond gas system and a mixer (none are shown) similarly as the deviceshown by the symbols 5 and 6 in FIG. 1, and the starting gas and thereaction gas are introduced into the reaction tube 50 through thestarting gas inlet 52. These gases react on the surface of the substrate57 during passage internally of the innerside reaction tube 51 as shownby the arrowhead 58 in FIG. 2 to deposit Al on the substrate surface.The gases after the reaction pass through the gap formed between theinnerside reaction tube 51 and the outside reaction tube 50, andevacuated through the gas evacuation outlet 53.

In taking out and in the substrate, the flange 54 made of a metal ispermitted to fall by an elevator (not shown) together with the substrateholding member 56 and the substrate 57 to be moved to a predeterminedposition where the substrate is mounted and detached.

By forming a deposited film under the conditions as described above byuse of such device, Al films of good quality can be formed in all thewafers within the device.

As described above, the film obtained according to the Al film formationprocess based on the embodiment of the present invention is dense withlittle content of impurity such as carbon, etc. and resistivity which issimilar to bulk, and also has high surface smoothness, and thereforeremarkable effects as described below can be obtained.

(1) Reduction of hillock

Hillock is occurrence of concavities on the Al surface due to partialmigration of Al when inner stress during film formation is released inthe heat treatment step. Also, similar phenomenon occurs by localmigration by current passage. The Al film formed by the presentinvention has little inner stress and is under the state of monocrystalor approximate to that. For this reason, in the heat treatment at 450°C. for one hour, as contrasted to formation of 10⁴ -10⁶ /cm² of hillocksin the Al film of the prior art, the hillock number could be greatlyimproved as 0 to 10/cm². Thus, due to substantial absence of Al surfaceconcavity, the resist film thickness and the interlayer insulating filmcan be made thin to be advantageous for making it finer and more flat.

(2) Improvement of electro-migration resistance

Electro-migration is the phenomenon that the wiring atoms move bypassage of a current of high density. By this phenomenon, voids aregenerated and grown along the grain boundary, whereby as accompaniedwith reduction of the cross-sectional area, the wiring generates heat tobe broken.

Migration resistance is generally evaluated by average wiring life.

The wiring formed by the sputtering method or the CVD method of theprior art has obtained an average wiring life of 1×10² to 10³ hours (inthe case of a wiring cross-sectional area of 1 μm²) under the currentpassage test conditions of 250° C., 1×10⁶ A/cm². In contrast, the Alfilm obtained by the Al film formation method based on the embodiment ofthe present invention could obtain an average wiring life of 10³ to 10⁴hours with a wiring having a cross-sectional area of 1 μm².

Hence, according to the present invention, for example, when the wiringwidth is 0.8 μm, a wiring layer thickness of 0.3 μm can sufficientlystand practical application. That is, since the wiring layer thicknesscan be made thinner, unevenness on the semiconductor surface afterarrangement of wiring can be suppressed minimum, and also highreliability in passing ordinary current can be obtained. Also, this ispossible by a very simple process.

(3) Improvement of surface smoothness (patterning characteristicimprovement of wiring)

In the prior art, roughness of the surface of a metal thin film hadinconvenience in the alignment step for the mask and the substrate inthe patterning step and in the etching step.

That is, there is unevenness extending to several μm on the surface ofAl film according to the prior art method, whereby the surfacemorphology is poor, and therefore had the following disadvantages.

1) Alignment signals cause diffused reflection to occur at the surface,whereby noise level becomes higher and inherent alignment signals cannotbe discriminated.

2) For covering large surface unevenness, the resist film thickness mustbe taken large, which is opposite to fine formation.

3) If the surface morphology is poor, halation due to the resistinternal reflection will occur locally, whereby resist remaining occurs.

4) If the surface morphology is poor, the side wall becomes notched inthe wiring etching step according to its unevenness.

According to the present invention, the surface morphology of Al film tobe formed is markedly improved to cancell all the drawbacks describedabove.

(4) Improvement of resistance in contact hole and through hole and ofcontact resistance

In the prior art method, if the size of the contact hole becomes fineras 1 μm×1 μm or less, Si in the wiring is precipitated on the substrateof the contact hole during heat treatment in the wiring step to coverthereover, whereby resistance between the wiring and the element becomesmarkedly larger.

According to the embodiment of the present invention, since a dense filmis formed according to the surface reaction, Al has been confirmed tohave a resistivity of 2.7-3.3 μohm cm. Also, the contact resistivity canattain 1×10⁻⁶ ohm.cm² at an area of 0.6 μm×0.6 μm when the Si portionhas an impurity of 10²⁰ cm⁻³.

That is, according to the present invention, a good contact with thesubstrate can be obtained.

In other words, in the patterning step, at the line width of theresolving power limit of the exposure machine, the alignment precision3σ=0.15 μm can be accomplished, whereby wiring having smooth side planeis rendered possible without causing halation to occur.

(5) It becomes possible to make heat treatment during wiring step loweror abolish the heat treatment step.

As described in detail above, by applying the present invention to thewiring formation method of a semiconductor integrated circuit, the yieldcan be improved, and reduction of cost can be promoted to great extentas compared with Al wiring of the prior art.

FIGS. 3A-3E show how the Al film according to the present invention isselectively grown.

FIG. 3A is an illustration showing schematically the cross-section ofthe substrate before formation of the Al deposited film according to thepresent invention. 90 is the substrate comprising an electron donativematerial, and 91 a thin film comprising an electron non-donativematerial.

In the case of using DMAH as the starting gas, when a gas mixturecontaining H₂ as the reaction gas is fed onto the substrate 1 heatedwithin a temperature range from the decomposition temperature of DMAH to450° C., Al is precipitated on the substrate 90, whereby a continuousfilm of Al is formed as shown in FIG. 3B. Here, the pressure within thereaction tube 2 should be desirably 10⁻³ to 760 Torr, and the DMAHpartial pressure preferably 1.5×10⁻⁵ to 1.3×10⁻³ -fold of the pressurewithin the above reaction tube.

When deposition of Al is continued under the above conditions, via thestate of FIG. 3C, the Al film grows to the level of the uppermostportion of the thin film 91 as shown in FIG. 3D. Further, when grownunder the same conditions, as shown in FIG. 3E, the Al film can grow to5000 Å substantially without growth in the lateral direction. This isthe most characteristic point of the deposited film obtained by thepresent invention, and it will be understood how a film of good qualitycan be formed under good selectivity.

As the result of analysis according to Auger's electron spectroscopy orphotoelectric spectroscopy, no entrainment of an impurity such as carbonor oxygen is recognized in this film.

The deposited film thus formed has a resistivity of, for example, with afilm thickness of 400 Å, 2.7-3.0 μohm.cm at room temperature which issubstantially equal to the bulk resistivity of Al, and becomescontinuous and flat film. Also, even with a film thickness of 1 μm, itsresistance at room temperature is approximately 2.7-3.0 μohm.cm and asufficiently dense film is formed with a relatively thicker film. Thereflectance in the visible wavelength region is approximately 80%, and athin film with excellent surface flatness can be deposited.

The substrate temperature in performing such selective deposition shouldbe desirably the decomposition temperature of the starting gascontaining Al or higher and 450° C. or lower as mentioned above, butspecifically a substrate temperature of 200° to 450° C. is desirable,and when deposition is performed under such condition, the depositionspeed is sufficiently great as 100 Å/min. to 800 Å/min. when DMAHpartial pressure is 10⁻⁴ to 10⁻³ Torr. Thus a sufficiently greatdeposition speed can be obtained as the Al deposition technique forultra-LSI.

A more preferable substrate temperature condition is 270° C. to 350° C.,and the Al film deposited under this condition is also stronglyorientatable and, even when subjected to the heat treatment at 450° C.for 1 hour, the Al film on the Si monocrystalline or Si polycrystallinesubstrate becomes a good Al film without generation of hillock, spike.Also, such Al film is excellent in electro-migration resistance.

Similarly in the case of selective deposition, in the device shown inFIG. 1, Al can be deposited on only one sheet of substrate in depositionfor one time. Although a deposition speed of ca. 800 Å/min. can beobtained, it is still insufficient for performing deposition of a largenumber of sheets within a short time.

As the deposition film forming device for improving this point, there isthe low pressure CVD device which can deposit Al by simultaneousmounting of a large number of sheets of wafer. Since the Al filmformation according to the present embodiment utilizes the surfacereaction of the electron donative substrate surface, in the hot walltype low pressure CVD method wherein only the substrate is heated, Alcan be deposited on the substrate by use of DMAH and H₂.

The reaction tube pressure may be 0.05 to 760 Torr, desirably 0.1 to 0.8Torr, the substrate temperature 160° C. to 450° C., desirably 200° C. to400° C., the DMAH partial pressure 1×10⁻⁵ -fold to 1.3×10⁻³ -fold of thepressure in the reaction tube, and under such conditions, Al can beselectively deposited on only the electron donative substrate.

The deposited film forming device to which such present invention isapplicable is the same as in FIG. 2 as described above, and thereforeits detailed description is omitted here.

By forming a deposited film under the conditions as described above byuse of such device, Al films of good quality can be formed selectivelyand simultaneously in all the wafers within the device.

As described above, the film obtained according to the Al film selectiveformation process based on the embodiment of the present invention isdense with very little content of impurity such as carbon, etc. andresistivity which is similar to bulk, and also has high surfacesmoothness, and therefore remarkable effects as described below can beobtained.

(1) Reduction of hillock

The Al film formed according to the present invention has littleinternal stress and is under the state of monocrystal or approximate tothat. For this reason, in the heat treatment at 450° C. for one hour, ascontrasted to formation of 10⁴ -10⁶ /cm² of hillrocks in the Al film ofthe prior art, the hillrock number could be greatly improved as 0 to10/cm².

(2) Improvement of electro-migration resistance

The wiring formed by the method of the prior art has obtained an averagewiring life of 1×10² to 10³ hours (in the case of a wiringcross-sectional area of 1 μm²) under the current passage test conditionsof 250° C., 1×10⁶ A/cm². In contrast, the Al film obtained by the Alfilm selective formation method based on the embodiment of the presentinvention could obtain an average wiring life of 10³ to 10⁴ hours with awiring having a cross-sectional area of 1 μm².

(3) Reduction of alloy pit in contact portion

The Al selectively formed according to the present invention cansuppress generation of alloy pit at the contact portion with thesubstrate crystal even by the heat treatment during wiring step, andalso a wiring with good contact characteristic can be obtained. That is,even when the junction is made shallow to the extent of 0.1 μm, thejunction will not be destroyed with only the Al material.

(4) Improvement of surface smoothness (patterning characteristicimprovement of wiring)

According to the present invention, the surface morphology of the Alfilm to be formed can be improved epoch-makingly, whereby all of theproblems of the prior art can be improved.

That is, in the patterning step, at the line width of the resolvingpower limit of the exposure machine, the alignment precision 3σ=0.15 μmcan be accomplished, whereby wiring having smooth side plane is renderedpossible without causing halation to occur.

(5) Improvement of resistance in contact hole and through hole andcontact resistance

According to the present invention, since adense film is selectivelyformed by the surface reaction even when the opening may be 1 μm×1 μm orless, it has been confirmed that the Al completely filled within thecontact hole and through hole each has a resistivity of 2.7-3.3 μohm.cm.Also, the contact resistivity can attain 1×10⁻⁶ ohm.cm² in the casewhere the Si portion has an impurity of 10²⁰ cm⁻³ in a hole of 0.6μm×0.6 μm.

That is, according to the present invention, the wiring material can becompletely embedded only in the minute opening, and also good contactwith the substrate can be obtained. Therefore, the present invention cancontribute greatly to improvement of resistance within hole and contactresistance which have been the greatest problems in the fine process of1 μm or less.

(6) It is possible to make the heat treatment temperature during wiringstep lower or to omit the heat treatment step.

As described in detail above, by applying the present invention to thewiring formation method of a semiconductor integrated circuit,particularly embedding of contact hole or through hole, the yield can beimproved, and reduction of cost can be promoted to great extent ascompared with Al wiring of the prior art.

EXAMPLE 1

First, the procedure for Al film formation is as follows. By use of thedevice shown in FIG. 1, the reaction tube 2 is internally evacuated toca. 1×10⁻⁸ Torr by the evacuation unit 9. However, Al film can be alsoformed if the vacuum degree within the reaction tube 2 may be higherthan 1×10⁻⁸ Torr.

After washing of Si wafer, the conveying chamber 10 is released toatmospheric pressure and Si wafer is mounted in the conveying chamber.The conveying chamber is evacuated to ca. 1×10⁻⁶ Torr, and then the gatevalve 13 is opened and the wafer is mounted on the wafer holder 3.

After mounting of the wafer on the wafer holder 3, the gate valve 13 isclosed, and the reaction chamber 2 is evacuated to a vacuum degree ofca. 1×10⁻⁸ Torr.

In this Example, DMAH is fed through the first gas line. As the carriergas of DMAH line H₂ which is the same as the reaction gas is employed.The second gas line is used for H₂.

By passing H₂ through the second gas line, the pressure within thereaction tube 2 is made a predetermined value by controlling the openingof the slow leak valve 8. A typical pressure in this Example is madeapproximately 1.5 Torr. Then, the wafer is heated by current passagethrough the heater 4. After the wafer temperature has reached apredetermined temperature, DMAH is introduced into the reaction tubethrough the DMAH line. The whole pressure is ca. 1.5 Torr, and the DMAHpartial pressure is made ca. 1.5×10⁻⁴ Torr. When DMAH is introduced intothe reaction tube 2, Al is deposited. After a predetermined depositiontime has elapsed, feeding of DMAH is stopped. Next, heating of theheater 4 is stopped to cool the wafer. Feeding of H₂ gas is stopped, andafter evacuation internally of the reaction tube, the wafer istransferred to the conveying chamber, and only the conveying chamber ismade atmospheric pressure before taking out the wafer. The outline of Alfilm formation is as described above.

EXPERIMENTAL EXAMPLE 1

Next, preparation of samples according to this Example 1 is described.

130 Sheets of samples of monocrystalline Si substrates (N type, 1-2ohm.cm) were prepared, the substrate temperatures were set at 13 levels,and Al films were deposited at the respective temperatures each for 10sheets according to the procedure as described above under the followingconditions:

whole pressure: 1.5 Torr

DMAH partial pressure: 1.5×10⁻⁴ Torr.

The Al films deposited by varying the substrate temperature at 13 levelswere evaluated by use of various evaluation methods. The results areshown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Evaluation                                                                           Substrate temperature (°C.)                                     item   150                                                                              160  200  250  270  300  330                                        __________________________________________________________________________    Carbon -- 0    0    0    0    0    0                                          content (%)                                                                   Resistivity                                                                          -- 2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                              (μΩ · cm)                                                   Reflectance                                                                          -- 85˜95                                                                        85˜95                                                                        85˜95                                                                        85˜95                                                                        85˜95                                                                        85˜95                                (%)                                                                           Average                                                                              -- 10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                   wiring                                                                        life (hour)                                                                   Deposition                                                                           -- 1˜9                                                                          100˜800                                                                      100˜800                                                                      100˜800                                                                      100˜800                                                                      100˜800                              Speed                                                                         (Å/min)                                                                   Hillock                                                                              -- .sup.  0˜10.sup.2                                                            .sup.  0˜10.sup.2                                                            .sup.  0˜10.sup.2                                                             0˜10                                                                         0˜10                                                                         0˜10                                density                                                                       (cm.sup.-2)                                                                   Spike  --  0˜10                                                                         0˜10                                                                        0    0    0    0                                          generation                                                                    ratio (%)                                                                     __________________________________________________________________________    Evaluation                                                                           Substrate temperature (°C.)                                     item   350  370    400 430   450  470                                         __________________________________________________________________________    Carbon 0    0     0    0     0    1˜9                                   content (%)                                                                   Resistivity                                                                          2.7˜3.3                                                                      2.7˜3.3                                                                       2.7˜3.3                                                                      2.7˜3.3                                                                       2.7˜3.3                                                                      2.7˜3.3                               (μΩ · cm)                                                   Reflectance                                                                          85˜95                                                                        85˜95                                                                         85˜95                                                                        70    60 or                                                                              60 or                                       (%)                          lower                                                                              lower                                       Average                                                                              10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                            10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.2                                                            10.sup.2 ˜10.sup.2                                                           10.sup.2 ˜10.sup.2                    wiring                                                                        life (hour)                                                                   Deposition                                                                           100˜800                                                                      100˜800                                                                       100˜800                                                                      100˜800                                                                       100˜800                                                                      1000                                        Speed                                                                         (Å/min)                                                                   Hillock                                                                               0˜10                                                                        .sup. .sup.  0˜10.sup.4                                                            .sup. .sup.  0˜10.sup.4                                                            .sup.  0˜10.sup.4                     density                                                                       (cm.sup.-2)                                                                   Spike  0     0˜30                                                                          0˜30                                                                         0˜30                                                                          0˜30                                                                         0˜30                                 generation                                                                    ratio (%)                                                                     __________________________________________________________________________     Note:                                                                         No deposition occurs at substrate temperature of 150° C.               Average wiring life is time to wire breaking when current is passed at a      current density of 1 × 10.sup.6 A/cm.sup.2 through a crosssectional     area of 1 μm.sup.2 at 250° C.                                       Spike generation ratio is destruction probability at the junction portion     of 0.15 μm depth.                                                     

Shortly speaking, Al films of very good quality were obtained at atemperature range of 160° C. to 450° C., more preferably 200° C. to 400°C., optimally 270° C. to 350° C.

EXAMPLE 2

First, the procedure of Al film formation is as follows. By theevacuation unit 9, the reaction tube 2 is evacuated internally to ca.1×10⁻⁸ Torr. Al film can be formed even if the vacuum degree in thereaction tube 2 may be higher than 1×10⁻⁸ Torr.

After washing of the Si wafer, the conveying chamber 10 is released toatmospheric pressure and the Si wafer is mounted in the conveyingchamber. The conveying chamber is evacuated to ca. 1×10⁻⁶ Torr, then thegate valve 13 is opened and the wafer is mounted on the wafer holder 3.

After mounting of the wafer holder 3, the gate valve 13 is closed, andthe reaction chamber 2 is evacuated to a vacuum degree of ca. 1×10⁻⁸Torr.

In this Example, the first gas line is used for DMAH. As the carrier gasfor the DMAH line, Ar is employed. The second gas line is used for H₂.

By passing H₂ through the second gas line, the pressure within thereaction tube 2 is made a predetermined value by controlling the openingof the slow leak valve 8. A typical pressure in this Example is madeapproximately 1.5 Torr. Then, the wafer is heated by current passagethrough the heater 4. After the wafer temperature has reached apredetermined temperature, DMAH is introduced into the reaction tubethrough the DMAH line. The whole pressure is ca. 1.5 Torr, and the DMAHpartial pressure is made ca. 1.5×10⁻⁴ Torr. When DMAH is introduced intothe reaction tube 2, Al is deposited. After a predetermined depositiontime has elasped, feeding of DMAH is stopped. Next, heating of theheater 4 is stopped to cool the wafer. Feeding of H₂ gas is stopped, andafter evacuation internally of the reaction tube, the wafer istransferred to the conveying chamber, and only the conveying chamber ismade atmospheric pressure before taking out the wafer. The outline of Alfilm formation is as described above.

EXPERIMENTAL EXAMPLE 2

Al films were formed according to the method of Example 2. For the filmsobtained, concerning resistivity, carbon content, average wiring life,deposition speed, hillock density, generation of spike and reflectance,the same results as in Example 1 were obtained.

EXAMPLE 3

This Example 3 performs deposition according to the same procedure byuse of MMAH₂ as the starting gas by setting the conditions as follows:

whole pressure: 1.5 Torr

MMAH₂ partial pressure: 5×10⁻⁴ Torr.

EXPERIMENTAL EXAMPLE 3

According to the method of the above Example 3, films were formed byvarying the substrate temperature within a temperature range from 160°C. to 400° C. As the result, Al thin films excellent in flatness,denseness containing no carbon impurity were deposited similarly as inExperimental example 1.

EXAMPLE 4

This Example 4 is film formation according to the low pressure CVDmethod.

EXPERIMENTAL EXAMPLE 4

A monocrystalline silicon substrate was placed in the low pressure CVDdevice shown in FIG. 2, and Al film was formed within the same badge.The film formation conditions were made a reaction tube pressure of 0.3Torr, a DMAH partial pressure of 3.0×10⁻⁵ Torr, a substrate temperatureof 300° C., and a film formation time of 10 minutes.

As the result of film formation under such conditions, an Al film of7000 Å was deposited. The film quality was very good, exhibiting thesame properties as one prepared at a substrate temperature of 300° C.shown in Experimental example 1.

EXPERIMENTAL EXAMPLE 5

Samples having Al films formed according to the same method as inExample 1 were prepared. When crystallinity of the Al film deposited onthe Si wafer of the respective samples, namely under the same filmforming conditions as in Example 1 by use of the X-ray diffractionmethod and the reflective electron beam diffraction method, it was foundto be a monocrystalline Al.

First, the evaluation methods are described.

When the crystal direction of the Si substrate is (111) plane, fromX-ray diffraction, as shown in FIG. 4, only the diffraction peak showingAl (100) was observed concerning Al. In reflective high speed electronbeam diffraction by use of an acceleration voltage of 80 kV or 100 kV,as shown in FIG. 5, a monocrystal spot showing Al (100) was observed.FIG. 5A is a diffraction pattern when electron beam is permitted toenter Al (100) in the [001] direction, FIG. 5B a diffraction patternwhen electron beam is permitted to enter Al (100) in the direction of[011]. Thus, the Al film on the Si (111) substrate was found to be amonocrystal having (100) plane. Within the substrate temperature rangein Table 1, particularly those deposited at a range from 250° C. to 330°C. were found to have Al films deposited which were stablymonocrystalline.

Also, the Al films deposited on the Si (111) substrate with thesubstrate surface having off-angles differing by 1°, 2°, 3°, 4°, 5° fromthe Si (111) plane were also found to have Al (100) monocrystalsdeposited stably, particularly under the temperature conditions of thesubstrate temperature ranging from 250° C. to 330° C., similarly as inthe case when deposited on the Si (111) substrate as described above.

When the crystal direction of the Si substrate is (100) plane, fromX-ray diffraction, as shown in FIG. 6, only the diffraction peak showingAl (111) was observed concerning Al. In reflective high speed electronbeam diffraction by use of an acceleration voltage of 80 kV or 100 kV, amonocrystal spot showing Al (111) was observed. Thus, the Al film on theSi (100) substrate was found to be a monocrystal having (111) plane.Within the substrate temperature range in Table 1, particularly thosedeposited at a range from 250° C. to 330° C. were found to have Al filmsdeposited which were stably monocrystalline. Also, the Al filmsdeposited on the Si (100) substrate with the substrate surface havingoff-angles differing by 1°, 2°, 3°, 4°, 5° from the Si (100) plane werealso found to have Al (111) monocrystals deposited stably, particularlyunder the temperature conditions of the substrate temperature rangingfrom 250° C. to 330° C., similarly as in the case when deposited on theSi (111) substrate as described above.

EXPERIMENTAL EXAMPLE 6

Crystallinities of the Al films formed according to the method ofExample 2 were evaluated. Similarly as in the case of Example 5,particularly within the range of the substrate temperature from 250° C.to 330° C., Al (100) monocrystal was formed on the Si (111) substrate,and Al (111) monocrystal on the Si (100) substrate.

EXPERIMENTAL EXAMPLE 7

Al films were formed on Si substrate according to the method of Example3. As the result of evaluation of crystallinities of the Al films by theX-ray diffraction method and the reflective high speed electron beamdiffraction method, the following results were obtained.

When the crystal direction of the Si substrate surface is (111) plane,from X-ray diffraction, as shown in FIG. 4, only the diffraction peakshowing Al (100) was observed concerning Al. In reflective high speedelectron beam diffraction by use of an acceleration voltage of 80 kV or100 kV, as shown in FIG. 5, a monocrystal spot showing Al (100) wasobserved. Thus, the Al film on the Si (111) substrate was found to be amonocrystal having (100) plane.

Also, the Al films deposited on the Si (111) substrate with thesubstrate surface having off-angles differing by 1°, 2°, 3°, 4°, 5° fromthe Si (111) plane were also found to have Al (100) monocrystalsdeposited, similarly as in the case when deposited on the Si (111)substrate as described above.

When the crystal direction of the Si substrate is (100) plane, fromX-ray diffraction, as shown in FIG. 6, only the diffraction peak showingAl (111) was observed concerning Al. In reflective high speed electronbeam diffraction by use of an acceleration voltage of 80 kV or 100 kV, amonocrystal spot showing Al (111) was observed. Thus, the Al film on theSi (100) substrate was found to be a monocrystal having (111) plane.Also, the Al films deposited on the Si (100) substrate with thesubstrate surface having offangles differing by 1°, 2°, 3°, 4°, 5° fromthe Si (100) plane were also found to have Al (111) monocrystalsdeposited, similarly as in the case when deposited on the Si (111)substrate as described above.

The Examples 5 to 8 and the Experimental examples 8 to 15 are exampleswhen forming Al films selectively.

EXAMPLE 5

First, the procedure of Al film formation according to this Example isas follows. By use of the device shown in FIG. 1, the reaction tube 2 isinternally evacuated to ca. 1×10⁻⁸ Torr by the evacuation unit 9.However, Al film can be also formed even if the vacuum degree within thereaction tube 2 may be higher than 1×10⁻⁸ Torr.

After washing of the Si wafer treated so as to effect selectivedeposition, the conveying chamber 10 is released to atmospheric pressureand the Si wafer is mounted in the conveying chamber. The conveyingchamber is evacuated to ca. 1×10⁻⁶ Torr, then the gate valve 13 isopened and the wafer is mounted on the wafer holder 3.

After mounting of the wafer on the wafer holder 3, the gate valve 13 isclosed, and the reaction chamber 2 is evacuated to a vacuum degree ofca. 1×10⁻⁸ Torr.

In this Example, DMAH is fed through the first gas line. As the carriergas of DMAH line, H₂ is employed. The second gas line is used for H₂. Bypassing H₂ through the second gas line, the pressure within the reactiontube 2 is made a predetermined value by controlling the opening of theslow leak valve 8. A typical pressure in this Example is madeapproximately 1.5 Torr. Then, the wafer is heated by current passagethrough the heater 4. After the wafer temperature has reached apredetermined temperature, DMAH is introduced into the reaction tubethrough the DMAH line. The whole pressure is ca. 1.5 Torr, and the DMAHpartial pressure is made ca. 1.5×10⁻⁴ Torr. When DMAH is introduced intothe reaction tube 2, Al is deposited. After a predetermined depositiontime has elapsed, feeding of DMAH is stopped. Next, heating of theheater 4 is stopped to cool the wafer. Feeding of H₂ gas is stopped, andafter evacuation internally of the reaction tube, the wafer istransferred to the conveying chamber, and only the conveying chamber ismade atmospheric pressure before taking out the wafer. The outline of Alfilm formation is as described above.

EXPERIMENTAL EXAMPLE 8

Si substrates (N type, 1-2 ohm.cm) were subjected to thermal oxidationat a temperature of 1000° C. according to the hydrogen combustion system(H₂ : 4 liters/M, O₂ : 2 liters/M).

The film thickness was 7000 Å±500 Å, and the reflactive index 1.46. Aphotoresist was coated on the whole Si substrate, and a desired patternwas baked by an exposure machine. The pattern was such that variousholes of 0.25 μm×0.25 μm-100 μm×100 μm were opened. After development ofthe photoresist, with the photoresist as the mask, the subbing SiO₂ wasetched by the reactive ion etching (RIE), etc. to have the substrate Sipartially exposed. Thus, 130 sheets of samples having various sizes ofSiO₂ holes of 0.25 μm×0.25 μm-100 μm×100 μm were prepared, the substratetemperature was set at 13 levels, and for the samples each of 10 sheetsat the respective temperatures, Al films were selectively depositedfollowing the procedure as described above under the followingconditions:

whole pressure: 1.5 Torr

DMAH partial pressure: 1.5×10⁻⁴ Torr.

The Al films deposited by varying the substrate temperature at 13 levelswere evaluated by use of various evaluation methods. The results areshown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________    Evaluation                                                                           Substrate temperature (°C.)                                     item   150                                                                              160  200  250  270  300  330                                        __________________________________________________________________________    Carbon -- 0    0    0    0    0    0                                          content (%)                                                                   Resistivity                                                                          -- 2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                                                                      2.7˜3.3                              (μΩ · cm)                                                   Reflectance                                                                          -- 85˜95                                                                        85˜95                                                                        85˜95                                                                        85˜95                                                                        85˜95                                                                        85˜95                                (%)                                                                           Average                                                                              -- 10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                   wiring                                                                        life (hour)                                                                   Deposition                                                                           -- 1˜9                                                                          100˜800                                                                      100˜800                                                                      100˜800                                                                      100˜800                                                                      100˜800                              Speed                                                                         (Å/min)                                                                   Hillock                                                                              -- .sup.  0˜10.sup.2                                                            .sup.  0˜10.sup.2                                                            .sup.  0˜10.sup.2                                                             0˜10                                                                         0˜10                                                                         0˜10                                density                                                                       (cm.sup.-2)                                                                   Spike  --  0˜10                                                                         0˜10                                                                        0    0    0    0                                          generation                                                                    ratio (%)                                                                     __________________________________________________________________________    Evaluation                                                                           Substrate temperature (°C.)                                     item   350  370    400 430   450  470                                         __________________________________________________________________________    Carbon 0    0     0    0     0    1˜9                                   content (%)                                                                   Resistivity                                                                          2.7˜3.3                                                                      2.7˜3.3                                                                       2.7˜3.3                                                                      2.7˜3.3                                                                       2.7˜3.3                                                                      2.7˜3.3                               (μΩ · cm)                                                   Reflectance                                                                          85˜95                                                                        85˜95                                                                         85˜95                                                                        70    60 or                                                                              60 or                                       (%)                          lower                                                                              lower                                       Average                                                                              10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.4                                                            10.sup.2 ˜10.sup.4                                                           10.sup.2 ˜10.sup.2                                                            10.sup.2 ˜10.sup.2                                                           10.sup.2 ˜10.sup.2                    wiring                                                                        life (hour)                                                                   Deposition                                                                           100˜800                                                                      100˜800                                                                       100˜800                                                                      100˜800                                                                       100˜800                                                                      1000                                        Speed                                                                         (Å/min)                                                                   Hillock                                                                               0˜10                                                                        .sup. .sup.  0˜10.sup.4                                                            .sup. .sup.  0˜10.sup.4                                                            .sup.  0˜10.sup.4                     density                                                                       (cm.sup.-2)                                                                   Spike  0     0˜30                                                                          0˜30                                                                         0˜30                                                                          0˜30                                                                         0˜30                                 generation                                                                    ratio (%)                                                                     __________________________________________________________________________     Note:                                                                         No deposition occurs at substrate temperature of 150° C.               Average wiring life is time to wire breaking when current is passed at a      current density of 1 × 10.sup.6 A/cm.sup.2 through a crosssectional     area of 1 μm.sup.2 at 250° C.                                       Spike generation ratio is destruction probability at the junction portion     of 0.15 μm depth.                                                     

In the above samples, no Al was deposited on SiO₂ at a temperature rangefrom 160° C. to 450° C., and Al was deposited only on the portion withopening of SiO₂ to have Si exposed. Also, when deposition was carriedout in the above temperature range continuously for 2 hours, similarselective depositability was maintained.

EXAMPLE 6

First, the procedure of Al film formation is as follows. By theevacuation unit 9, the reaction tube 2 is evacuated internally to ca.1×10⁻⁸ Torr. Al film can be formed even if the vacuum degree in thereaction tube 2 may be higher than 1×10⁻⁸ Torr.

After washing of the Si wafer, the conveying chamber 10 is released toatmospheric pressure and the Si wafer is mounted in the conveyingchamber. The conveying chamber is evacuated to ca. 1×10⁻⁶ Torr, then thegate valve 13 is opened and the wafer is mounted on the wafer holder 3.

After mounting of the wafer on the wafer holder 3, the gate valve 13 isclosed and the reaction chamber 2 is evacuated to a vacuum degree of ca.1×10⁻⁸ Torr.

In this Example, the first gas line is used for DMAH. As the carrier gasfor the DMAH line, Ar is employed. The second gas line is used for H₂.

by passing H₂ through the second gas line, the pressure within thereaction tube 2 is made a predetermined value by controlling the openingof the slow leak valve 8. A typical pressure in this Example is madeapproximately 1.5 Torr. Then, the wafer is heated by current passagethrough the heater 4. After the wafer temperature has reached apredetermined temperature, DMAH is introduced into the reaction tubethrough the DMAH line. The whole pressure is ca. 1.5 Torr, and the DMAHpartial pressure is made ca. 1.5×10⁻⁴ Torr. When DMAH is introduced intothe reaction tube 2, Al is deposited. After a predetermined depositiontime has elapsed, feeding of DMAH is stopped. Next, heating of theheater 4 is stopped to cool the wafer. Feeding of H₂ gas is stopped, andafter evacuation internally of the reaction tube, the wafer istransferred to the conveying chamber, and only the conveying chamber ismade atmospheric pressure before taking out the wafer. The outline of Alfilm formation is as described above.

EXPERIMENTAL EXAMPLE 9

Al films were formed according to the method of Example 6. For the filmsobtained, concerning resistivity, carbon content, average wiring life,deposition speed, hillock density, generation of spike and reflectance,the same results as in Experimental example 8 were obtained.

Also, selective depositability with substrate was the same as inExperimental example 8.

EXAMPLE 7

This Example is selective deposition of Al according to the low pressureCVD method.

EXPERIMENTAL EXAMPLE 10

By means of the low pressure CVD device shown in FIG. 2, Al films wereformed on the substrates with the constitutions as described below(Samples 5-1-5-179).

PREPARATION OF SAMPLE 5-1

On a monocrystalline silicon as the electron donative first substratesurface material, a thermally oxidized SiO₂ film as the electronnon-donative second substrate surface material was formed, andpatterning was effected according to the photolithographic steps asshown in Example 1 to have the monocrystalline surface partiallyexposed.

The film thickness of the thermally oxidized SiO₂ film was found to be7000 Å, with the size of the exposed portion of the monocrystallinesilicon, namely opening being 3 μm×3 μm. Thus, Sample 5-1 was prepared.(Hereinafter, such sample is expressed as "thermally oxidized SiO₂(hereinafter abbreviated as T-SiO₂)/monocrystalline silicon").

PREPARATION OF SAMPLES 5-2-5-179

Sample 5-2 is an oxidized film formed by normal pressure CVD(hereinafter abbreviated as SiO₂)/monocrystalline silicon.

Sample 5-3 is a boron doped oxidized film formed by normal pressure CVD(hereinafter abbreviated as BSG)/monocrystalline silicon.

Sample 5-4 is a phosphorus doped oxidized film formed by normal pressureCVD (hereinafter abbreviated as PSG)/monocrystalline silicon.

Sample 5-5 is a phosphorus and boron doped oxidized film formed bynormal pressure CVD (hereinafter abbreviated as BSPG)/monocrystallinesilicon.

Sample 5-6 is a nitrided film formed by plasma CVD (hereinafterabbreviated as P-S:N)/monocrystalline silicon.

Sample 5-7 is a thermally nitrided film (hereinafter abbreviated asT-S:N)/monocrystalline silicon.

Sample 5-8 is a nitrided film formed by low pressure CVD (hereinafterabbreviated as LP-S:N)/monocrystalline silicon.

Sample 5-9 is a nitrided film formed by ECR device (hereinafterabbreviated as ECR-SiN)/monocrystalline silicon.

Further, by combinations of the electron donative first substratesurface materials and the electron non-donative second substrate surfacematerials, Samples 5-11-5-179 shown in Table 3 were prepared. As thefirst substrate surface material, monocrystalline silicon(monocrystalline Si), polycrystalline silicon (polycrystalline Si),amorphous silicon (amorphous Si), tungsten (W), molybdenum (Mo),tantalum (Ta), tungsten silicide (WSi), titanium silicide (TiSi),aluminum (Al), aluminum silicon (Al-Si), titanium aluminum (Al-Ti),titanium nitride (TiN), copper (Cu), aluminum silicon copper (Al-Si-Cu),aluminum palladium (Al-Pd), titanium (Ti), molybdenum silicide (Mo-Si),tantalum silicide (Ta-Si) were employed. These samples and Al₂ O₃substrates, SiO₂ glass substrates were placed in the low pressure CVDdevice shown in FIG. 2, and Al films were formed within the same badge.The film forming conditions were a reaction tube pressure of 0.3 Torr, aDMAH partial pressure of 3.0×10⁻⁵ Torr, a substrate temperature of 300°C. and a film formation time of 10 minutes.

As the result of film formation under such conditions, concerning allthe samples applied with patterning from Sample 5-1 to 5-179, depositionof Al film occurred only on the electron donative first substratesurface film to embed completely the opening with the depth of 7000 Å.The film quality of the Al film was found to be very good, exhibitingthe same properties as one prepared at a substrate temperature of 300°C. shown in Experimental example 8. On the other hand, on the secondsubstrate surface which is electron non-donative, no Al film wasdeposited at all, whereby complete selectivity was obtained. On both theAl₂ O₃ substrate and the SiO₂ glass substrate which are electronnon-donative, no Al film was deposited at all.

EXPERIMENTAL EXAMPLE 11

By use of the low pressure CVD device shown in FIG. 2, Al film wasformed on the substrate with the constitution as described below.

On a thermally oxidized film as the electron non-donative secondsubstrate surface material, a polycrystalline Si as the electrondonative first substrate surface material was formed, patterning waseffected according to the photolithographic steps as shown in Example 1to have the thermally oxidized film surface partially exposed. The filmthickness of the polycrystalline silicon at this time was 2000 Å, withthe size of the thermally oxidized film exposed portion, namely openingbeing 3 μm×3 μm. Such sample is called 6-1. By combinations of theelectron non-donative second substrate surface materials (T-SiO₂,CVD-SiO₂, BSG, PSG, BPSG, P-SiN, T-SiN, LP-SiN, ECR-S:N) and theelectron-donative first substrate surface materials (polycrystalline Si,amorphous Si, Al, W, Mo, Ta, WSi, TiSi, TaSi, Al-Si, Al-Ti, TiN, Cu,Al-Si-Cu, Al-Pd, Ti, Mo-Si), Samples of 6-1-6-169 shown in Table 3 wereprepared. These samples were placed in the low CVD device shown in FIG.2, and Al film was formed within the same badge. The film formingconditions were a reaction tube pressure of 0.3 Torr, a DMAH partialpressure of 3.0×10⁻⁵ Torr, a substrate temperature of 300° C. and a filmforming time of 10 minutes. As the result of film formation under suchconditions, in all the samples from 6-1 to 6-169, no Al film wasdeposited at all at the opening having the electron non-donative secondsubstrate exposed, but Al of about 7000 Å was deposited only on theelectron donative first substrate, whereby complete selectivity wasobtained. The film quality of the Al film deposited was found to be verygood, exhibiting the same properties as one prepared at a substratetemperature of 300° C. in Experimental example 1.

                                      TABLE 3                                     __________________________________________________________________________         Mono-                                                                             Poly-                                                                     crystal-                                                                          Crystal-                                                                           Amor-                                                                line                                                                              line phous                                                                Si  Si   Si  W  Mo Ta WSi                                                                              TiSi                                                                             Al AlSi                                      __________________________________________________________________________    T-SiO.sub.2                                                                        5-1 5-11 5-21                                                                              5-31                                                                             5-41                                                                             5-51                                                                             5-61                                                                             5-71                                                                             5-81                                                                             5-91                                      SiO.sub.2                                                                          5-2 5-12 5-22                                                                              5-32                                                                             5-42                                                                             5-52                                                                             5-62                                                                             5-72                                                                             5-82                                                                             5-92                                      BSG  5-3 5-13 5-23                                                                              5-33                                                                             5-43                                                                             5-53                                                                             5-63                                                                             5-73                                                                             5-83                                                                             5-93                                      PSG  5-4 5-14 5-24                                                                              5-34                                                                             5-44                                                                             5-54                                                                             5-64                                                                             5-74                                                                             5-84                                                                             5-94                                      BPSC 5-5 5-15 5-25                                                                              5-35                                                                             5-45                                                                             5-55                                                                             5-65                                                                             5-75                                                                             5-85                                                                             5-95                                      P-SiN                                                                              5-6 5-16 5-26                                                                              5-36                                                                             5-46                                                                             5-56                                                                             5-66                                                                             5-76                                                                             5-86                                                                             5-96                                      T-SiN                                                                              5-7 5-17 5-27                                                                              5-37                                                                             5-47                                                                             5-57                                                                             5-67                                                                             5-77                                                                             5-87                                                                             5-97                                      LP-SiN                                                                             5-8 5-18 5-28                                                                              5-38                                                                             5-48                                                                             5-58                                                                             5-68                                                                             5-78                                                                             5-88                                                                             5-98                                      ECR-SiN                                                                            5-9 5-19 5-29                                                                              5-39                                                                             5-49                                                                             5-59                                                                             5-69                                                                             5-79                                                                             5-89                                                                             5-99                                      __________________________________________________________________________                      Al--                                                             AlTi                                                                              Ti--N                                                                              Cu  Si--Cu                                                                            AlPd                                                                              Ti  Mo--Si                                                                             Ta--Si                                     __________________________________________________________________________    T-SiO.sub.2                                                                        5-101                                                                             5-111                                                                              5-121                                                                             5-131                                                                             5-141                                                                             5-151                                                                             5-161                                                                              5-171                                      SiO.sub.2                                                                          5-102                                                                             5-112                                                                              5-122                                                                             5-132                                                                             5-142                                                                             5-152                                                                             5-162                                                                              5-172                                      BSG  5-103                                                                             5-113                                                                              5-123                                                                             5-133                                                                             5-143                                                                             5-153                                                                             5-163                                                                              5-173                                      PSG  5-104                                                                             5-114                                                                              5-124                                                                             5-134                                                                             5-144                                                                             5-154                                                                             5-164                                                                              5-174                                      BPSG 5-105                                                                             5-115                                                                              5-125                                                                             5-135                                                                             5-145                                                                             5-155                                                                             5-165                                                                              5-175                                      P-SiN                                                                              5-106                                                                             5-116                                                                              5-126                                                                             5-136                                                                             5-146                                                                             5-156                                                                             5-166                                                                              5-176                                      T-SiN                                                                              5-107                                                                             5-117                                                                              5-127                                                                             5-137                                                                             5-147                                                                             5-157                                                                             5-167                                                                              5-177                                      LP-SiN                                                                             5-108                                                                             5-118                                                                              5-128                                                                             5-138                                                                             5-148                                                                             5-158                                                                             5-168                                                                              5-178                                      ECR-SiN                                                                            5-109                                                                             5-119                                                                              5-129                                                                             5-139                                                                             5-149                                                                             5-159                                                                             5-169                                                                              5-179                                      __________________________________________________________________________     (note) Numeral shows sample No.                                          

                                      TABLE 4                                     __________________________________________________________________________          Poly-                                                                         Crystal-                                                                           Amor-                                                                    line phous                                                                    Si   Si  W  Mo Ta  WSi                                                                              TiSi                                                                             Al AlSi                                        __________________________________________________________________________    T-SiO.sub.2                                                                         6-1  6-11                                                                              6-21                                                                             6-31                                                                             6-41                                                                              6-51                                                                             6-61                                                                             6-71                                                                             6-81                                        SiO.sub.2                                                                           6-2  6-12                                                                              6-22                                                                             6-32                                                                             6-42                                                                              6-52                                                                             6-62                                                                             6-72                                                                             6-82                                        BSG   6-3  6-13                                                                              6-23                                                                             6-33                                                                             6-43                                                                              6-53                                                                             6-63                                                                             6-73                                                                             6-83                                        PSG   6-4  6-14                                                                              6-24                                                                             6-34                                                                             6-44                                                                              6-54                                                                             6-64                                                                             6-74                                                                             6-84                                        BPSC  6-5  6-15                                                                              6-25                                                                             6-35                                                                             6-45                                                                              6-55                                                                             6-65                                                                             6-75                                                                             6-85                                        P-SiN 6-6  6-16                                                                              6-26                                                                             6-36                                                                             6-46                                                                              6-56                                                                             6-66                                                                             6-76                                                                             6-86                                        T-SiN 6-7  6-17                                                                              6-27                                                                             6-37                                                                             6-47                                                                              6-57                                                                             6-67                                                                             6-77                                                                             6-87                                        LP-SiN                                                                              6-8  6-18                                                                              6-28                                                                             6-38                                                                             6-48                                                                              6-58                                                                             6-68                                                                             6-78                                                                             6-88                                        ECR-SiN                                                                             6-9  6-19                                                                              6-29                                                                             6-39                                                                             6-49                                                                              6-59                                                                             6-69                                                                             6-78                                                                             6-89                                        __________________________________________________________________________                     Al--                                                               AlTi                                                                             Ti--N                                                                             Cu  Si--Cu                                                                            AlPd                                                                             Ti  Mo--Si                                                                             Ta--Si                                       __________________________________________________________________________    T-SiO.sub.2                                                                         6-91                                                                             6-101                                                                             6-111                                                                             6-121                                                                             6-131                                                                            6-141                                                                             6-151                                                                              6-161                                        SiO.sub.2                                                                           6-92                                                                             6-102                                                                             6-112                                                                             6-122                                                                             6-132                                                                            6-142                                                                             6-152                                                                              6-162                                        BSG   6-93                                                                             6-103                                                                             6-113                                                                             6-123                                                                             6-133                                                                            6-143                                                                             6-153                                                                              6-163                                        PSG   6-94                                                                             6-104                                                                             6-114                                                                             6-124                                                                             6-134                                                                            6-144                                                                             6-154                                                                              6-164                                        BPSG  6-95                                                                             6-105                                                                             6-115                                                                             6-125                                                                             6-135                                                                            6-145                                                                             6-155                                                                              6-165                                        P-SiN 6-96                                                                             6-106                                                                             6-116                                                                             6-126                                                                             6-136                                                                            6-146                                                                             6-156                                                                              6-166                                        T-SiN 6-97                                                                             6-107                                                                             6-117                                                                             6-127                                                                             6-137                                                                            6-147                                                                             6-157                                                                              6-167                                        LP-SiN                                                                              6-98                                                                             6-108                                                                             6-118                                                                             6-128                                                                             6-138                                                                            6-148                                                                             6-158                                                                              6-168                                        ECR-SiN                                                                             6-99                                                                             6-109                                                                             6-119                                                                             6-129                                                                             6-139                                                                            6-149                                                                             6-159                                                                              6-169                                        __________________________________________________________________________     (note) Numeral shows sample No.                                          

EXAMPLE 8

This Example is the method of depositing selectively Al by use of MMAH₂.

EXPERIMENTAL EXAMPLE 12

When deposition was carried out according to the same procedure as shownin Example 1 by use of MMAH₂ as the starting gas and setting theconditions as follows:

whole pressure: 1.5 Torr

MMAH₂ partial pressure: 5×10⁻⁴ Torr,

in the temperature range of the substrate temperature from 160° C. to400° C., an Al thin film containing no carbon impurity and havingexcellent flatness, denseness and selectivity with the substrate surfacematerials was deposited similarly as in Example 1.

EXPERIMENTAL EXAMPLE 13

According to the same method as in Example 5, a sample having an Al filmformed thereon was prepared. The crystallinity of the Al filmselectively deposited on Si at the same substrate temperature as inTable 1 was evaluated by the X-ray diffraction method and the scanningμ-RHEED microscope.

The scanning μ-RHEED microscope is the method disclosed in ExtendedAbstracts of the 21th Conference on Solid State Devices and Materials(1989) p.217 and Japanese Journal of Applied Physics vol. 28, No. 11(1989), L2075. According to the RHEED (Reflection High Energy ElectronDiffraction) method of prior art, electron beam was permitted to beincident on the sample surface at a shallow angle of 2°-3°, and thecrystallinity of the sample surface was evaluated from the diffractionpattern formed by the diffracted electron beam. However, since theelectron beam diameter is large as 100 μm to several hundred μm, onlyaverage information on the sample surface could be obtained. In theμ-RHEED microscope, an electron beam diffraction pattern from a specificfine region on the sample surface can be observed by narrowing theelectron beam diameter of 0.1 μm. Also, by scanning the electron beamtwo-dimensionally on the sample surface, by use of any desireddiffraction spot intensity change on the diffraction pattern as theimage signal, two dimensional image (scanning μ-RHEED image) on thesample surface can be obtained. At this time by observation of thescanning μ-RHEED image by use of different diffraction spots A and C onthe diffraction pattern as shown in FIG. 7, even if the lattice planesin parallel to the sample surface may be aligned in (100), the crystalgrain boundaries rotating within the plane can be visualized asdistinguished from each other. Here, the diffraction spot A is adiffraction spot on the line (line 1) where the plane in which thediffraction pattern occurs and the sagittal plane formed by the incidentelectron beam are crossed at right angle, while the diffraction spot Cis a diffraction spot not on the line 1. As shown in FIG. 8, when thelattice plane in parallel to the sample surface is, for example, (100),but crystal grains x and y are rotating mutually within the plane, inthe scanning μ-RHEED image by use of the diffraction spot A, bothcrystal grains x and y are displayed as the region with strongintensity. On the other hand, in the scanning μ-RHEED image by use ofthe diffraction spot C, only the crystal grain x is displayed as theregion with strong intensity. Therefore, by observation of the scanningμ-RHEED image by use of the diffraction spots A and C as shown in FIG.7, it can be discriminated whether the crystal in the region observed isa polycrystal including interplanar rotation or a monocrystal. InExtended Abstracts of the 21th Conference on Solid State Devices andMaterials (1989 ) p.217 and Japanese Journal of Applied Physics vol. 28,No. 11 (1989) L2075, concerning Cu thin film, it has been clarifiedthat, for example, even if the lattice plane in parallel to the samplesurface may be {100}, there exists a crystal grain including interplanarrotation in the {100} crystal grains.

First, the Al film deposited selectively on the Si exposed surface atthe substrate temperature in Table 1 was evaluated.

When the crystal direction on the Si substrate surface is (111) plane,from X-ray diffraction, concerning Al, as shown in FIG. 9, only thediffraction peak showing Al (100) could be observed. Next, crystallinityof the Al film deposited selectively was evaluated by use of a scanningμ-RHEED microscope. As shown in FIG. 10, after the region where Al hadbeen selectively deposited was specified by the scanning secondaryelectron image showing the surface form (FIG. 10A), by use of thediffraction spot 200 (corresponding to the diffraction spot A in FIG. 7)and the diffraction spot 620 (corresponding to the diffraction spot C inFIG. 7) on the diffraction pattern occurring when the electron beam waspermitted on the Al (100) plane from the [001] direction, the scanningμ-RHEED image (FIG. 10B) and FIG. 10C) was observed. As shownschematically in FIG. 10B and FIG. 10C, there is no change in lightnessand darkness on the Al film selectively deposited, and the Alselectively deposited was confirmed to be an Al (100) monocrystal.

On the other hand, when the Si exposed plane is not linear but likevia-hole, irrespectively of the via-hole diameter, the Al selectivelydeposited was found to be similarly Al (100) monocrystal. Those atsubstrate temperatures ranging from 250° C. to 330° C. were selectivelydeposited stably, and the Al obtained was found to become monocrystal.

Also, Al films deposited selectively on the Si (111) substrate with theSi (111) plane being at off-angles by 1°, 2°, 3°, 4°, 5° from the Sisubstrate were also found to deposit Al (100) monocrystals under thetemperature conditions of the substrate temperature ranging from 250° C.to 330° C. similarly as deposited on the Si (111) substrate as describedabove.

When the crystal direction of the Si substrate surface is the (100)plane, from X-ray diffraction, concerning Al, as shown in FIG. 11, onlythe diffraction peak showing Al (111) could be observed. FIG. 12 showsthe scanning secondary electron image (FIG. 12A) and the scanningμ-RHEED image (FIGS. 12B and 12C) when Al was selectively deposited ononly the Si exposed surface on a substrate having Si (100) exposed in aline by patterning of SiO₂ in a line. For the scanning μ-RHEED image,the 333 diffraction spots (FIG. 12B) and 531 diffraction spots (FIG.12C) were employed. The Al film selectively deposited was confirmed tobe an Al (111) monocrystal. Those at substrate temperatures ranging from250° C. to 330° C. were found to be selectively deposited stably, andthe Al films obtained became monocrystals.

Also, Al films deposited selectively on the Si (100) substrate with theSi (100) plane being at off-angles by 1°, 2°, 3°, 4°, 5° from the Sisubstrate surface were also found to deposit Al (111) monocrystals underthe temperature conditions of the substrate temperature ranging from250° C. to 330° C. similarly as deposited on the Si (111) substrate asdescribed above.

EXPERIMENTAL EXAMPLE 14

Crystallinity of the Al film deposited selectively according to the samemethod as shown in Example 6 was evaluated. Similarly as in Experimentalexample 8, at substrate temperatures ranging from 250° C. to 330° C., Al(100) monocrystals on the Si (111) substrate and Al (111) monocrystalson Si (100) substrate were obtained stably.

EXPERIMENTAL EXAMPLE 15

Crystallinity of the Al film deposited selectively according to the samemethod as shown in Example 7 was evaluated.

From the scanning μ-RHEED microscope observation according to the sameobservation method as described in Experimental example 13, when thefirst substrate material is Si (111), in either case when the secondsubstrate material is T-SiO₂, SiO₂, BSG, PSG, BPSG, P-SiN, T-Si-N,LP-SiN or ECR-SiN, the Al selectively deposited on Si was found to be Al(100). When the first substrate material is Si (100), in either casewhen the substrate material is T-SiO₂, SiO₂, BSG, PSG, BPSG, P-SiN,T-SiN, LP-SiN or ECR-SiN, the Al film selectively deposited was found tobe Al (111).

When the first material is TiN, in either case when the second substratematerial is T-SiO₂, SiO₂, BSG, PSG, BPSG, P-SiN, T-SiN, LP-SiN orECR-SiN, the Al film selectively deposited on TiN was found to beoriented in Al (111) from X-ray diffraction, and from reflective highspeed electron beam diffraction pattern of the prior art by use of anelectron beam of an acceleration voltage of 80 kV or 100 kV, diffractionspots concerned with Al (111) were strongly observed.

COMPARATIVE EXPERIMENT

An Al film was formed on a monocrystalline silicon under the followingconditions.

By passing Ar in place of H₂, Al was deposited by pyrolysis of DMAH. Thetotal pressure at this time was made 1.5 Torr, the DMAH partial pressure1.5×10⁻⁴ Torr, and the substrate temperature of 270°-350° C.

When the Al film thus formed was evaluated, about 2% of carbon was foundto be contained at the minimum.

Resistivity became greater by 2-fold or more than the case when hydrogenwas employed.

As to reflectance, it was lowered to about 1/3 to 1/9 relative the casewhen hydrogen was employed.

Similarly, wiring life was shorter by 1 to 2 cipher, generationprobability of hillock became greater by 2 cipher or more, and a largenumber of spikes were found to be generated.

As to the deposition speed, it was lowered to 1/2 to 1/4.

As described above, Al deposited only by decomposition of DMAH withoutuse of H₂ is inferior in film quality, and was unsatisfactory as the Alfilm for a semiconductor device.

Separately, without use of H₂, DMAH was decomposed by the optical CVDmethod to deposit Al. As the result, same improvement such as nocontainment of carbon, and the like was observed from the Al filmprepared as compared with the case when no light was employed, but othercharacteristics were not improved so much, and the Al film was stillunsatisfactory as the Al film for a semiconductor device.

As described above, the mechanism of Al deposition according to thepresent invention may be presently hypothesized as follows.

When DMAH reaches the electron donative substrate, namely the substratehaving electrons under the state on which hydrogen atoms are attached(FIG. 13A) with the methyl groups directed toward the substrate side,one electron of the substrate cut one bond of Al and methyl group (FIGS.13B, 13C).

The reaction scheme at this time is as follows:

    (CH.sub.3).sub.2 AlH+2H+2e→2CH.sub.4 ↑+Al-H.

Further, similar reactions will proceed for the hydrogen atoms remainingon deposited Al having free electrons (FIG. 13D). Here, when hydrogenatoms are deficient, hydrogen molecules constituting the reaction gasare decomposed on the substrate to suppy hydrogen atoms. On the otherhand, since there is no electron on the electron non-donative surface,the above-mentioned reaction will not proceed and no Al deposited.

FIGS. 13A-13D are illustrations for better understanding of the reacionmechanism, and the numbers of H, e and Al shown in FIGS. 13A-13D are notnecessarily coincident.

As described above, according to the present invention, a lowresistivity, dense and flat Al film could be deposited on a substrate.

Also, depending on the kind of the substrate, deposition can be effectedselectively.

What we claim is:
 1. A process for forming a deposited film comprising the steps of:(a) providing a substrate having an electron donative surface (A) in a space for formation of the deposited film, (b) introducing a gas of the an alkyl aluminum hydride and hydrogen gas into said space for formation of deposited film, and (c) maintaining the temperature of said electron donative surface (A) within the range of from the decomposition temperature of said alkyl aluminum hydride to 450° C. to form an aluminum film on said electron donative surface (A).
 2. The process according to claim 1, wherein said alkyl aluminum hydride is dimethyl aluminum hydride.
 3. The process according to claim 1, wherein said alkyl aluminum hydride is monomethyl aluminum hydride.
 4. The process according to claim 1, wherein said substrate is formed of a material selected from monocrystalline silicon, polycrystalline silicon and amorphous silicon.
 5. The process according to claim 1, wherein said substrate is a III-V compound semiconductor containing an element belonging to the group III of the periodic table and an element belonging to the group V of the periodic table.
 6. The process according to claim 1, wherein said substrate is a II-VI compound semiconductor containing an element belonging to the group II of the periodic table and an element belonging to the group VI of the periodic table.
 7. The process according to claim 1, wherein said substrate is a metal containing at least one element selected from tungsten, molybdenum, tantalum, aluminum, titanium and copper.
 8. The process according to claim 1, wherein said substrate is a metal.
 9. The process according to claim 1, wherein said substrate is a semiconductor.
 10. The process according to claim 1, wherein said substrate is silicide.
 11. The process according to claim 1, wherein said aluminum film is monocrystalline.
 12. A process for forming a deposited film comprising the steps of:(a) providing a substrate having an electron donative surface (A) and an electron non-donative surface (B) in a space for formation of the deposited film, (b) introducing a gas of an alkyl aluminum hydride and hydrogen gas into said space for formation of the deposited film, and (c) maintaining the temperature of said electron donative surface (A) within the range of from the decomposition temperature of said alkyl aluminum hydride to 450° C. to form an aluminum film selectively on said electron donative surface (A).
 13. The process according to claim 12, wherein said alkyl aluminum hydride is dimethyl aluminum hydride.
 14. The process according to claim 12, wherein said alkyl aluminum hydride is monomethyl aluminum hydride.
 15. The process according to claim 12, wherein said electron donative surface (A) is formed of a material selected from monocrystalline silicon, polycrystalline silicon and amorphous silicon, and said electron non-donative surface (B) is formed of an insulating material.
 16. The process according to claim 12, wherein said electron donative surface (A) is formed of a III-V group compound semiconductor containing an element belonging to the group III of the periodic table and an element belonging to the group V of the periodic table, and said electron non-donative surface (B) is formed of an insulating material.
 17. The process according to claim 12, wherein said electron donative surface (A) is formed of a II-VI group compound semiconductor containing an element belonging to the group II of the periodic table and an element belonging to the group VI of the periodic table, and said electron non-donative surface (B) is formed of an insulating material.
 18. The process according to claim 12, wherein said electron donative surface (A) is formed of a metal containing at least one element selected from tungsten, molybdenum, tantalum, aluminum, titanium and copper, and said electron non-donative surface (B) is formed of an insulating material.
 19. The process according to claim 12, wherein said electron donative surface (A) is formed of a metal and said electron non-donative surface (B) is formed of an insulating material.
 20. The process according to claim 12, wherein said electron donative surface (A) is formed of a semiconductor and said electron non-donative surface (B) is formed of an insulating material.
 21. The process according to claim 12, wherein said electron donative surface (A) is formed of silicide and said electron non-donative surface (B) is formed of an insulating material. 